96365 reports the first 16 to 90 minutes of an IV infusion of a therapeutic, prophylactic, or diagnostic drug or substance — the non-chemo half of the infusion coding world. 96366 is the “each additional hour” add-on that bills, in units, every hour beyond the first when the time exceeds 30 minutes. Together they capture the full duration of non-chemo biologic infusions like Remicade, Ocrevus, Rituxan (non-oncologic), Stelara IV, Soliris, Entyvio, and IVIG. The most common biller error is omitting 96366 add-on units entirely on multi-hour infusions, leaving facility revenue on the floor; the second most common is using 96365 when the drug actually meets the chemo administration definition and 96413 was the right code.
96365 and 96366 are part of the AMA CPT 96360-96379 intravenous infusion family. The AMA CPT manual defines 96365 as “Intravenous infusion, for therapy, prophylaxis, or diagnosis (specify substance or drug); initial, up to 1 hour” and 96366 as “each additional hour (List separately in addition to code for primary procedure).” The descriptors place them in opposition to the 96401-96549 chemotherapy administration family: 96413 is the chemo analog of 96365, and 96415 is the chemo analog of 96366. The decision between the two families is the single most consequential coding decision on a non-oncology specialty drug claim.
Medicare billing rules for these codes live in CMS IOM Pub 100-04, Chapter 12 (Physicians/Nonphysician Practitioners), §30.5, and the NCCI bundling and modifier rules in the current-year NCCI Policy Manual for Medicare Services Chapter XI (Medicine). AMA coding guidance in CPT Assistant has clarified the “greater than 30 minutes beyond the prior hour” rule (sometimes called the ≥31-minute rule) for the 96366 add-on. Most commercial payers have aligned to the CMS rules; the small payer-to-payer variance is captured in the per-payer grid below.
The decision tree is mechanical because both the AMA descriptor and the NCCI edits are mechanical. In practice, the highest-volume 96365 drug families are anti-TNF biologics (Remicade, Simponi Aria), anti-CD20 monoclonals given for non-oncologic indications (Ocrevus, Rituxan for RA/lupus), interleukin inhibitors given IV (Stelara IV), complement inhibitors (Soliris, Ultomiris), gut-tropic biologics (Entyvio), and the entire IVIG class (Privigen, Gammagard, Octagam, Gamunex-C, Panzyga). Each of these generates a multi-hour infusion the majority of the time, so the 96366 add-on lines do most of the time-based revenue work on the encounter.
The most painful version of misuse is the chemo/non-chemo classification flip: billing 96365 for an oncologic Rituxan when 96413 was correct (or vice versa) under-bills the practice and triggers a payer audit when the J-code (J9312 for Rituxan) is cross-referenced against the diagnosis code (C-series for lymphoma vs M-series for RA). The classification follows AMA's complexity definition and the documented indication, not the practice's preference.
The top five payers all recognize 96365/96366 as CMS does. Variance is small and concentrated around hour-counting strictness, NCCI overlay enforcement, and the chemo/non-chemo classification of a handful of edge-case monoclonals (Rituxan being the canonical example).
| Payer | 96365/96366 recognized? | Notes |
|---|---|---|
| Medicare (Part B) | Yes — standard payment under MPFS | Source-of-truth payer. MACs publish LCDs naming 96365 as the correct administration code for the LCD-covered drugs (e.g., IVIG LCD L33610 series). NCCI edits enforce 96366 only as add-on to 96365 or 96413. The ≥31-minute rule for 96366 is the operative interpretation in CMS audits. |
| UnitedHealthcare | Yes | Aligns with CMS. Adds a post-payment audit overlay that flags 96366 units exceeding the documented infusion stop-time minus start-time. Optum infusion-management prior auths name 96365 as the expected primary code; deviation requires reauthorization. |
| Aetna (CVS Health) | Yes | Aligns with CMS. Aetna medical-policy bulletins for biologic infusions explicitly list 96365 as the expected code. CVS Specialty infused-meds workflow assumes 96365 + 96366 sequencing. |
| Cigna / Express Scripts | Yes | Aligns with CMS. Accredo dispensing report does not include the administration code (it is on the buy-and-bill medical claim only). The infusion suite bills 96365/96366 directly to Cigna under medical benefit. |
| Humana | Yes | MA-heavy book follows CMS by default. CenterWell Home Infusion bills 96365/96366 to Humana under the medical benefit; the home-infusion S-code overlay (S5497-S5523 family) applies in addition for the per-diem nursing piece on home infusion encounters. |
| Denial pattern | What it means | Fix / appeal language |
|---|---|---|
| 96413 billed for a non-chemo biologic (CARC 16) | Chemo administration code billed when the drug actually meets the AMA non-chemo definition. Diagnosis code (e.g., M05.x for RA, K50.x for Crohn's, G35 for MS) does not support chemo classification. | Resubmit with 96365 + 96366 add-on units instead of 96413/96415. Appeal language: “Per AMA CPT chemotherapy administration definition, this encounter does not meet the complex preparation / extended observation / chemo-toxicity criteria for 96413. The corrected claim reports [drug] under 96365 + 96366 × [n] consistent with the documented infusion time of [X] minutes and the non-oncologic indication of [ICD-10].” |
| 96365 + 96366 sequence error (CARC 4 / NCCI bundle) | 96366 reported without 96365 (or 96413) as the primary procedure. Add-on codes cannot stand alone — NCCI rejects. | Resubmit with 96365 as the initial-service code and 96366 as the add-on. Verify the documented infusion time supports the 96365 + 96366 sequence (16+ minutes for 96365, plus 91+ minutes total for the first 96366). Appeal language: “CPT 96366 is reported as the add-on to CPT 96365 per AMA descriptor. The corrected claim sequences both codes consistent with the documented [X]-minute infusion.” |
| 96366 under-counted (no denial — under-billed claim) | Multi-hour infusion submitted with 96365 only or with fewer 96366 units than the documented time supports. No payer denial, but practice loses facility revenue on every encounter. The most common silent under-billing in non-chemo infusion coding. | Audit each multi-hour 96365 encounter and submit a corrected claim with the additional 96366 units. Appeal language: “The original claim reported 96365 + 96366 × [n] for an infusion documented as [X] minutes. Per the AMA 'each additional hour' rule (more than 30 minutes beyond the prior reported hour), the documented time supports 96366 × [n+m]. The corrected claim adds [m] additional unit(s) of 96366.” |
| Two 96365 codes on same encounter (NCCI bundle) | 96365 billed twice in one encounter for two different drugs. The 96365 / 96366 family permits only one initial-service code per encounter. | Resubmit with the second drug as 96367 (sequential infusion, additional drug, up to 1 hour). If the second drug is concurrent (running through a different lumen at the same time), use 96368. Appeal language: “Per AMA CPT infusion hierarchy, only one initial-service code is reportable per encounter. The corrected claim reports [drug 1] as 96365 + 96366 and [drug 2] as 96367 sequential.” |
| 96365 + 96360 same encounter (NCCI bundle) | Hydration billed alongside a non-chemo drug infusion where the hydration was just the drug carrier fluid or a routine flush. NCCI edits reject the 96360 as bundled into 96365. | Drop 96360/96361 unless the hydration was medically necessary beyond drug delivery, documented as separate infusion time, and supported by a hydration-specific ICD-10 (E86.0 dehydration, etc.). Appeal language only if separately documented: “The hydration of [X] minutes from [start] to [stop] was medically necessary for [diagnosis ICD-10] beyond the drug carrier fluid, documented as a distinct infusion run with separate start/stop times. Per NCCI Ch.XI, separately reportable hydration is not bundled into 96365.” |
96365 is for therapeutic, prophylactic, or diagnostic non-chemo IV infusions — biologics like Remicade, Ocrevus, Rituxan, Stelara IV, IVIG, and Soliris. 96413 is for anti-neoplastic drugs and monoclonal antibodies that meet the AMA chemotherapy administration definition (complex preparation, extended observation, or chemo-like toxicity). The classification follows the AMA definition, not the drug's primary indication, and is the single most common biller error in this code family.
The first 16 to 90 minutes of infusion are reported as 96365 (the initial hour). Each additional hour beyond the first 90 minutes is reported as one unit of 96366, with the additional time needing to exceed 30 minutes beyond the prior reported hour. So an infusion lasting 91 to 150 minutes is 96365 + 96366 × 1; 151 to 210 minutes is 96365 + 96366 × 2; 211 to 270 minutes is 96365 + 96366 × 3; and so on.
The first hour for 96365 is the first 16 to 90 minutes of the infusion. An infusion shorter than 16 minutes is reported as an IV push (96374 or 96375), not as 96365. An infusion lasting 16 to 90 minutes is exactly one unit of 96365 with no 96366. The 90-minute upper bound is what triggers the first 96366 add-on — the 91st minute does not generate an add-on; it takes another 30+ minutes beyond 90 to get to the ≥31-minute threshold for the first add-on hour.
One initial-service code per encounter. If two non-chemo biologics are infused sequentially, 96365 reports the first drug's initial hour (with 96366 for additional hours), and 96367 reports the sequential second drug. If a chemo drug is also infused, the chemotherapy code 96413 takes the initial-service slot regardless of drug order, and the non-chemo biologic becomes 96367 sequential. See the 96367/96368 deep-dive for the full sequencing rules.
The AMA CPT chemotherapy administration definition includes monoclonal antibodies used in anti-neoplastic treatment (e.g., Rituxan for lymphoma is billed as chemo administration when given for oncologic indication, but as non-chemo 96365 when given for rheumatoid arthritis). The classification follows the indication and complexity of preparation/observation, not the drug name. Industry convention: trastuzumab, bevacizumab, pembrolizumab, nivolumab — chemo (96413). Infliximab, ocrelizumab, ustekinumab IV, IVIG — non-chemo (96365). Rituxan crosses the line depending on indication and is the canonical edge case.
Yes. The push (96374 or 96375) and the infusion (96365 with 96366 add-ons) are both reportable in the same encounter when they deliver different drugs. The initial-service code is the highest hierarchy item: chemotherapy > therapeutic infusion > IV push > hydration. If a pre-medication is pushed and then a non-chemo biologic is infused, the infusion is the initial-service code (96365) and the push is reported as 96375 (each additional new drug push, since the infusion has already taken the initial-service slot).
No. 96365 reports time and route, not anatomic site. Bilateral and anatomic modifiers (RT/LT/E1-E4, modifier 50) attach to procedure codes with anatomic specificity. The IV infusion itself does not have anatomic laterality for billing purposes; the access site is documented in the medical record but not coded with a side modifier on 96365.
Hydration is bundled into 96365 when the IV fluid is the carrier for the drug or routine flush. If a separately medically necessary hydration runs >30 min before or after the drug infusion (e.g., pre-cisplatin protective hydration), the hydration is billable with 96360 + 96361 add-ons, but the drug infusion is still the initial-service code 96365 (or 96413 for chemo). The hydration code becomes the secondary line, not the initial service.
All sources are publicly available federal publications or paraphrased from professional-society educational materials. The methodology by which we resolve source disagreements is described in the Methodology.